DS200TBQDG1AFF gas turbine electric card

 Each communication interface connected to the Advant Fieldbus 100 supports a module status word. The status word is a two byte entity indicating whether the communication interface has a valid configuration, is able to share the bus master responsibilities, and if it wants to update the configuration of sending CDPs. The module status is a facility which is used among the communication interfaces only. It has no significance for the CDP communication and message transfer at all. When a communication interface is bus master, it periodically attempts reading the module status of all possible modules attached to the Advant Fieldbus 100. It thus obtains information about which communication interfaces are available, and which state they are in. The module status is read by sending a master frame with function code 15. The address/control field contains the address of the designated communication interface. If the communication interface is present, it answers with a slave frame containing the module status word (that is two bytes of data).

Bus Master Transfer 

At the end of every 1024, 2048 or 4096 millisecond cycle, time is determined by the CDP with the longest cycle time, the bus master attempts to transfer the bus master responsibilities to the next communication interface in line. The pass-over is a twostep algorithm which also includes synchronization between all communication interfaces. Figure 112 shows the scenario where the bus master (with address 2) tries to transfer the bus master responsibilities to another communication interface, which is an active bus administrator (with address 3).The bus master first sends a master frame with function code 8, and its own address in the address/control field. It responds itself with a two byte slave frame containing a check sum of the current configuration. The master frame is always transmitted at a fixed time in the last time slot. The reception of this frame can thus be used for synchronization of the internal timers in all communication interfaces. Furthermore, the slave frame is used to check the validity of the configuration.

Now, the bus master sends a new master frame with function code 8 and the address of the communication interface to take over in the address/control field. This communication interface responds with a slave frame containing its own view of the current configuration (that is the check sum). If the check sum matches that of the previous slave frame, the pass-over is successful, and the new communication interface takes over the bus master responsibilities. Otherwise, the old bus master remains bus master for another 1024, 2048 or 4096 millisecond cycle